Light scattered from an object contains both amplitude and phase information. This amplitude and phase information can be captured on, for example, a photosensitive plate by well known interference techniques to form a hologram comprising interference fringes. The hologram may be reconstructed to form an image, or holographic reconstruction, representative of the original object by illuminating the hologram with suitable light.
Computer-generated holography may numerically simulate the interference process using Fourier techniques.
It has been proposed to use holographic techniques in a two-dimensional image projector.
Referring to FIG. 1, there is shown a light source 100 which applies light via a Fourier lens (120) onto a spatial light modulator (140) in this case as a generally planar wavefront. The spatial light modulator is reflective and consists of an array of a large number of phase-modulating elements. Light is reflected by the spatial light modulator and consists of two parts, a first specularly reflected portion (known as the zero order) and a second portion that has been modulated by the phase-modulating elements to form a wavefront of spatially varying phase. Due to the reflection by the spatial light modulator all of the light is reflected generally back towards the light source (100) where it impinges on a mirror with aperture (160) disposed at 45° to the axis of the system. All of the image part of the light is reflected by the mirror towards a screen (180) that is generally parallel to the axis of the system. Due to the action of the Fourier lens (120), the light that impinges on the screen (180) forms a real image that is a reconstruction of an image from which the information applied to the phase modulating elements was derived.
Embodiments relate to an improved 2D real-time projector for forming virtual images of holographic reconstructions and providing adaptive positional control of the virtual image in space, and allow for spatial filtering of the reconstruction.